Two-Electron Transfer Reactions in Electrochemistry for Solution-Soluble and Surface-Confined Molecules: A Common Approach

Abstract

In this paper, the general characteristics of the normalized voltammetric response for reversible two-electron transfer reactions (EE mechanism) is analyzed and particularized to the application of derivative normal pulse voltammetry (dNPV) using electrodes of any geometry and size, and cyclic voltammetry (CV), when the molecule undergoing the process is soluble in solution and surface-confined, respectively. The analysis is based on the close relationships between the electrochemical response and the theoretical values of surface concentrations/excesses, and has led to the voltammetric signal of the EE mechanism being interpreted in terms of the percentage of E 1e − E 1e − , and E 2e − character, as a function of the difference between the formal potentials of both electron transfers, ΔE 0 ′ = E 2 0 ′ − E 1 0 ′. In line with the percentage of E 2e − character, the term "effective electron number", n eff , has been introduced and related to the probability of the second electron being transferred in an apparently simultaneous way with the first one and a direct method to obtain the values of E 1 0 ′ and E 2 0 ′ for any ΔE 0 ′ has been proposed. The key role of ΔE 0 ′ (in mV, 25 °C) = −142.4, −71.2, −35.6, and 0 values in the behavior of the peak parameters of the voltammetric curves is explained in terms of the usual terminology (transition 2 peaks−1 peak, repulsive− attractive interactions, anticooperativity−cooperativity, and normal-inverted order of potentials). The EE mechanism is also compared with two independent E mechanisms (E+E).

Models and Their Limitations in the Voltammmetric Parameterization of the Six‐Electron Surface‐Confined Reduction of [PMo12O40]3− at Glassy Carbon and Boron‐Doped Diamond Electrodes

“…The aspect of agreement in both studies at BDD in 1 M HClO 4 is that differences in ΔE1, DE 2 and DE 3 are small. Furthermore, we note that simulated data when potentials of E 0 1 and E 0 2 are similar [9,[37][38][39] are not highly sensitive to ΔE variation which leads to uncertainties for experimentalists in heuristic forms of data analysis, as noted in this study. It is also probable that greater uncertainties are present in the method used by Molina et al [11] compared to our data optimization approach.…”

Dynamics of Interfacial Electron Transfer from Betanin to Nanocrystalline TiO2: The Pursuit of Two-Electron Injection

“…53,54 In this case the one-electron oxidation product should be thermodynamically unstable to disproportionation: 2Bt…”

Integration of Heuristic and Automated Parametrization of Three Unresolved Two‐Electron Surface‐Confined Polyoxometalate Reduction Processes by AC Voltammetry

“…Further points for noting which can be gained from perusal of Figure and which need to be accommodated in simulation‐experiment comparisons are that the first two processes partially overlap, Process II has a larger peak current magnitude than either Processes I or III and the shapes of all three process differ. Importantly, for each of the three reduction steps it has been proposed,, that two unresolved reversible one electron transfer steps of purely adsorbed material occur as in Eq. 5– …”